Xie Min, Shen Zhitao, Wang Dandan, Fujii Asuka, Lee Yuan-Pern
Department of Applied Chemistry and Institute of Molecular Science , National Chiao Tung University , 1001 Ta-Hsueh Road , Hsinchu 30010 , Taiwan.
Department of Chemistry , Graduate School of Science, Tohoku University , Sendai 980-8578 , Japan.
J Phys Chem Lett. 2018 Jul 5;9(13):3725-3730. doi: 10.1021/acs.jpclett.8b01491. Epub 2018 Jun 25.
The three-electron two-center (3e-2c) bond plays an important role in structures and electron communication in biological systems involving cationic sulfur compounds. Although the nature of 3e-2c bonds and their theoretical formalism have attracted great interest, direct spectral identifications of 3e-2c-bound molecules are scarce. We observed the infrared spectra of the weakly 3e-2c-bound CHS∴S(H)CH and the strongly 3e-2c-bound (CHSH) in a supersonic jet using infrared (IR) dissociation with vacuum-ultraviolet photoionization and time-of-flight detection. Protonation of CHS∴S(H)CH to form [CH(H)S∴S(H)CH] significantly enhances the 3e-2c bond, characterized by a large red shift of the SH-stretching band with enhanced IR intensity, shortening of the calculated S-S distance from 3.00 to 2.86 Å, and a dissociation energy increased from ∼23 to 162 kJ mol.
三电子双中心（3e-2c）键在涉及阳离子硫化合物的生物系统的结构和电子通讯中起着重要作用。尽管3e-2c键的性质及其理论形式已引起了极大关注，但对3e-2c键合分子的直接光谱鉴定却很稀少。我们在超声速射流中，利用红外（IR）解离结合真空紫外光电离和飞行时间检测，观测了弱3e-2c键合的CHS∴S(H)CH和强3e-2c键合的(CHSH)的红外光谱。CHS∴S(H)CH质子化形成[CH(H)S∴S(H)CH]显著增强了3e-2c键，其特征为SH伸缩带大幅红移且红外强度增强、计算出的S-S距离从3.00 Å缩短至2.86 Å，以及解离能从约23 kJ mol增加至162 kJ mol。
